NHC metal (silver, mercury, and nickel) complexes based on quinoxaline-dibenzimidazolium salts: Synthesis, structural studies, and fluorescent chemosensors for Cu2+ by charge transfer

Article abstract of DOI:10.1021/om400277z

The two dibenzimidazolium salts 2,3-bis[(1-ⁿPr- benzimidazoliumyl)methyl]quinoxaline hexafluorophosphate (H₂-1a) and 2,3-bis[(1-Pi-benzimidazoliumyl)methyl]quinoxaline hexafluorophosphate (H ₂-1b) (ⁿPr = n-propyl and Pi = picolyl) and their four NHC metal complexes [Ag₂(1a)₂](PF₆)₂ (2a), [Hg(1a)(OAc)(H₂O)]₂(PF₆)₂ (2b), [Ag₂(1b)₂](PF₆)₂ (2c) and [Ni(1b)](NiCl₄) (2d) have been synthesized and characterized. Each cation in 2a,c possesses a boxlike structure with different sizes. In 2b, one 18-membered macrometallacycle is formed by two bidentate NHC ligands and two mercury(II) atoms, in which an inversion center is observed. In 2d, one nickel(II) atom is surrounded by two carbene carbon atoms and two nitrogen atoms from two pyridine rings to adopt a square geometry. The recognition of Cu ²⁺ using 2a,c as chemosensors by charge transfer was investigated on the basis of fluorescence and UV/vis spectroscopic titrations. The results show that complexes 2a,c are effective chemosensors for Cu²⁺.

Full text of DOI:10.1021/om400277z

om-2013-00277z
Supporting Information
NHC Metal (Ag, Hg and Ni) Complexes Based on Quinoxaline-dibenzimidalium
2
+
Salts: Synthesis, Structural Studies and Fluorescent Chemosensors for Cu by
Charge Transfer
QingꢀXiang Liu*, ZhaoꢀQuan Yao, XiaoꢀJun Zhao, ZhiꢀXiang Zhao and XiuꢀGuang
Wang
Table of contents
1
2
3
4
. Deriving the equation for 1:1 association curve fitting.
. Tables S1ꢀS3.
. The figures of crystal structrures of 2b and 2c (Figure S1 and Figure S2).
. The figures of fluorescence and UV/vis spectroscopies for 2a and 2c (Figure S3
and Figure S4).
1
2+
2+
5
6
7
. The figures of H NMR, infrared and mass spectra for 2a, 2c, 2a/Cu and 2c/Cu
(
Figure S5ꢀFigure S11).
1
13
. The figures of H and C NMR spectra for organic intermediate and complexes
2
aꢀ2d.
. The crystal packings of complexes 2aꢀ2d.
1

1
. Deriving the equation for 1:1 association curve fitting
R + G
RG
K
R is receptor, G is guest molecule or ion, and K is the association constant. The
total concentration of the receptor is [R ], and the equilibrated concentrations of guest,
receptor and RG following each titration are [G], [R] and [RG], respectively.
] = [R] + [RG]
K = [RG]/[R][G]
RG] = K[R][G]
When the absorbance of all the species is much less than 0.1, the fluorescence
intensity is linearly proportional to the concentration of fluorescing species. Define F
0
[R
0
[
0
as the fluorescence intensity of the free receptor, and F as the fluorescence intensity of
the receptor/guest complex:
F
0
= k
r 0
[R ]
F = k [R] + krg[RG]
r
ꢁ
F = F ꢀ F = k [R] + k [RG] ꢀ k [R ] = k ([R ] – [RG]) + k [RG] ꢀ k [R ]
0
r
rg
r
0
r
0
rg
r
0
=
(krg ꢀ k
r
)[RG]
N 0 0
To facilitate the deriving, to set up: ꢁF = (F ꢀ F )/(Fmax – F )
ꢁ
F = (F ꢀ F )/(F – F ) = (k ꢀ k )[RG]/ (k ꢀ k )[RG] = [RG]/[RG]max
N
0
max
0
rg
r
rg
r
max
0
When the fluorescence intensity of receptor reach the max, [RG]max ≈ [R ]
ꢁ
F
N
N
= [RG]/[RG]max = [RG]/[R
0
] = [RG]/([R] + [RG]), because [RG] = K[R][G]
ꢁF
= K[R][G]/([R] + K[R][G]) = K[G]/(1 + K[G])
1
/ꢁF
N
N
= 1 + 1/K[G]
ꢀ 1 = 1/K[G]
1
/ꢁF
We get the logarithmic on the both side of this equation
ln(1/ꢁF ꢀ 1) = ln(1/K[G]) = ꢀ(lnK + ln[G])
N
To match with the symbol in the origin plots, to define ln[G] = X
N
ln(1/ꢁF ꢀ 1) = ꢀ(lnK + X)
ꢀ(lnK + X)
1
/ꢁF – 1 = e
N
ꢀ(lnK + X)
ꢁF
N
= 1/(1+ e
0 0
) = (F ꢀ F )/(Fmax – F )
2

ꢀ(lnK + X)
F = F
0
+ (Fmax – F
0
)/(1 + e
)
In this equation F and F are the fluorescence intensity of receptor in the
0
presence and absence of guest, respectively, Fmax is final flourecence intensity in
titration experiment, X means ln[G], and K is the association constant.
2
. Tables S1-S3
Table S1. In the same ligand of 2aꢀ2d, the dihedral angles (˚) between two
benzimidazole rings (A), and the dihedral angles (˚) between quinoxaline
ring and two benzimidazole rings (B)
Complexes
A
B
2
2
a
35.6(1) 77.4(1), 80.2(3)
25.1(4) 81.3(7), 83.4(1)
24.9(1) 68.8(1), 77.5(8)
56.9(9) 83.9(1), 89.4(1)
b
2
c
2
d
3

Table S2. Summary of crystallographic data for 2a and 2b
2
aꢂCH
3
4 10
CNꢂC H O
2
2bꢂ5H O
C
60
H
60Ag
2
F
12
N
12
P
2
64 70 12 2 6 2 12
C H N Hg O P F
ꢂ8CH OH
3
chemical formula
ꢂCH
3
CNꢂC
4
H
10
O
fw
1569.05
1948.69
Triclinic
Pī
Cryst syst
space group
a/Å
Orthorhombic
P212121
18.949(2)
13.064(1)
27.660(4)
90
13.077(1)
13.824(1)
14.191(1)
87.2(2)
72.1(2)
68.9(2)
2272.7(4)
1
b/Å
c/Å
α/deg
β/deg
γ/deg
90
90
3
V/Å
6847.2(1)
4
Z
3
D
calcd, Mg/m
1.522
1.424
ꢀ1
Abs coeff, mm
F(000)
0.704
3196
0.704
974
Cryst size, mm
0.15 × 0.14 × 0.13 0.15 × 0.14 × 0.13
θ
min, θmax, deg
1.47, 25.00
296(2)
34655
12066
872
1.89, 25.01
173(2)
11368
7881
T /K
no. of data collected
no. of unique data
no. of refined params
501
2
a
goodnessꢀofꢀfit on F
1.056
1.064
b
Final R indices [I > 2σ(I)]
R1
0.0371
0.0915
0.0349
0.0966
wR2
R indices (all data)
R1
0.0411
0.0944
0.0393
0.0987
wR2
a
2
o
2 2
1/2
GOF = [Σω(F ꢀ F ) /(nꢀp)] , where n is the number of reflection and p is the
c
b
2
2 2
number of parameters refined.
R
1
o c o 2 o c
= Σ(||F | ꢀ |F ||)/Σ|F |; wR =[Σ[w(F ꢀ F ) ]/
2
2 1/2
o
Σw(F ) ] .
4

Table S3．Summary of crystallographic data for 2c and 2d
2
2
cꢂH O
2 3 2
2dꢂ4H Oꢂ4(CH ) SO
72 8 4
C H56Cl N16Ni
chemical formula
36 6 8 2
C H28AgF N PꢂH O
2 3 2
ꢂ4H Oꢂ4(CH ) SO
fw
843.52
Monoclinic
/c
2048.34
Cryst syst
space group
a/Å
Monoclinic
C
2
1
P2 /c
18.123(2)
23.008(3)
17.223(1)
90
17.979(8)
31.232(1)
15.858(7)
90
b/Å
c/Å
α/deg
β/deg
γ/deg
90
90
90
90
3
V/Å
7181.9(1)
8
8905(8)
4
Z
3
D
calcd, Mg/m
1.560
1.528
ꢀ1
Abs coeff, mm
F(000)
0.680
3408
1.230
4224
Cryst size, mm
0.15 × 0.14 × 0.13
1.43, 25.01
173(2) K
17731
0.15 × 0.14 × 0.13
1.30, 25.00
173(2)
θ
min, θmax, deg
T /K
no. of data collected
no. of unique data
no. of refined params
20388
6272
4035
499
322
2
a
goodnessꢀofꢀfit on F
1.073
1.160
b
Final R indices [I > 2σ(I)]
R1
0.0795
0.1937
0.1331
0.2770
wR2
R indices (all data)
R1
0.0853
0.1971
0.1574
0.2939
wR2
a
2
o
2 2
1/2
GOF = [Σω(F ꢀ F ) /(nꢀp)] , where n is the number of reflection and p is the
c
b
2
2 2
number of parameters refined.
R
1
o c o 2 o c
= Σ(||F | ꢀ |F ||)/Σ|F |; wR =[Σ[w(F ꢀ F ) ]/
2
2 1/2
o
Σw(F ) ] .
5

3
. The figures of crystal structrures of 2b and 2c
Figure S1. Perspective view of 2c and anisotropic displacement parameters depicting
0% probability. All hydrogen atoms were omitted for clarity. Selected bond lengths
Å) and angles (˚): Ag(1)ꢀC(16) 2.102(7), Ag(1)ꢀC(30A) 2.040(9);
5
(
C(16)ꢀAg(1)ꢀC(30A) 176.3(3), N(3)ꢀC(16)ꢀN(4) 106.8(6).
Figure S2. A view of 2b along c axis.
6

4
. The figures of fluorescence and UV/vis spectroscopies for 2a and 2c
ꢀ5
Figure S3(a). UV/vis absorption change of 2a (1 × 10 mol/L) upon the addition of
+
+
+
+
4
2+
3+
2+
2+
+
2+
2+
the nitrate salts of Li , Na , K , NH
, Ca , Al , Zn , Cd , Ag , Pb , Co ,
2
+
2+
ꢀ5
Ni and Cu (5 × 10 mol/L) in acetonitrile at 25 ˚C.
2
+
Figure S3(b). The curve of fluorescence intensity vs lnCCu at 495 nm for 2a; the
curve fit using a 1:1 association equation (1).
7

2
+
Figure S3(c). Emission (at 495 nm) of 2a at different concentrations of Cu (0, 0.05,
0.1, 0.5, 1.0 ꢃM) added, normalized between the minimum emission (0.0 ꢃM
2
+
2+
Cu ) and the emission (1.0 ꢃM Cu ). The detection limit was determined to
ꢀ8
be 5.0 × 10 mol/L.
Figure S3(d). Change ratio ((F
i
ꢀF
0
)/(FCu2+ꢀF
0
)) of fluorescence intensity of 2a (1.0 ×
ꢀ5
ꢀ5
1
0 mol/L) at 495 nm in various mixtures of metal ions (Cu(NO ) 5.0 × 10
3 2
ꢀ5
2+
mol/L and another metal ion 5.0 × 10 mol/L). Background cations. 1: Cu ;
2
+
+
2+
+
2+
+
2+
+
2+
2+
2
4
: Cu + Li ; 3: Cu + Na ; 4: Cu + K ; 5: Cu + NH ; 6: Cu + Ca ; 7:
2
+
3+
2+
2+
2+
2+
2+
+
2+
2+
Cu + Al ; 8: Cu + Zn ; 9: Cu + Cd ; 10: Cu + Ag ; 11: Cu + Pb ;
2+
2+
2+
2+
1
2: Cu + Co ; 13: Cu + Ni in acetonitrile at 25 ˚C.
8

ꢀ5
Figure S4(a). UV/vis absorption change of 2c (1 × 10 mol/L) upon the addition of
+
+
+
+
4
2+
3+
2+
2+
+
2+
2+
the nitrate salts of Li , Na , K , NH
, Ca , Al , Zn , Cd , Ag , Pb , Co ,
2
+
2+
ꢀ5
Ni and Cu (5 × 10 mol/L) in acetonitrile at 25 ˚C.
2
+
Figure S4(b). Fluorescence intensity at 490 nm vs lnCCu for 2c; the curve fit using a
1:1 association equation (1).
9

2
+
Figure S4(c). Emission (at 490 nm) of 2c at different concentrations of Cu (0, 0.01,
0.05, 0.1, 0.5, 1.0 ꢃM) added, normalized between the minimum emission
2
+
2+
(
0.0 ꢃM Cu ) and the emission (1.0 ꢃM Cu ). The detection limit was
ꢀ8
determined to be 1.0 × 10 mol/L.
2+
Figure S4(d). Change ratio ((F ꢀF )/(F ꢀF )) of fluorescence intensity of 2c (1.0 ×
i
0
Cu
0
ꢀ5
ꢀ5
1
3 2
0 mol/L) at 490 nm in various mixtures of metal ions (Cu(NO ) 5.0 × 10
ꢀ5
2+
mol/L and another metal ion 5.0 × 10 mol/L). Background cations. 1: Cu ;
2
+
+
2+
+
2+
+
2+
+
2+
2+
2
: Cu + Li ; 3: Cu + Na ; 4: Cu + K ; 5: Cu + NH ; 6: Cu + Ca ; 7:
4
2
+
3+
2+
2+
2+
2+
2+
+
2+
2+
Cu + Al ; 8: Cu + Zn ; 9: Cu + Cd ; 10: Cu + Ag ; 11: Cu + Pb ;
10

2+
2+
2+
2+
1
2: Cu + Co ; 13: Cu + Ni in acetonitrile at 25 ˚C.
1
2+
5
. The figures of H NMR, infrared and mass spectra for 2a, 2c, 2a/Cu and
2
+
2c/Cu
1
1
Figure S5. H NMR (400 MH
Z 6
, DMSOꢀd ): the changes of H NMR spectra in
2+
2+
aromatic rings for 2a and 2a/Cu . a: complex 2a, b: 2a/Cu .
1
1
Figure S6. H NMR (400 MH
Z 6
, DMSOꢀd ): the changes of H NMR spectra in
2
+
2+
aromatic rings for 2c and 2c/Cu . a: complex 2c, b: 2c/Cu .
11

3 2
Figure S7. Infrared spectra of Cu(NO ) .
Figure S8. Infrared spectra of complex 2a and 2a/Cu(NO ) .
3
2
Figure S9. Infrared spectra of complex 2c and 2c/Cu(NO3)2.
12

ꢀ
6
+
Figure S10. Mass spectrum of complex 2a. MS (EI): m/z {[Mꢀ2(PF
)]/2} = 582.45.
ꢀ
+
Figure S11. Mass spectrum of complex 2c. MS (EI): m/z {[Mꢀ2(PF
6
)]/2} = 680.60.
13

1
13
6
. The Figures of H and C NMR spectra for organic intermediate and
complexes 2a-2d
14

15

16

17

18

7
. The crystal packings of complexes 2a-2d.
The Crystal Packings of Complexes 2a-2d. In the crystal packing of 2a (Figure
ꢀ
S12(a)), 2D supramolecular layer is formed by cations and PF
6
through CꢀHꢂꢂꢂF
1
2
hydrogen bonds and CꢀHꢂꢂꢂπ contacts. In the CꢀHꢂꢂꢂF hydrogen bonds, the hydrogen
atoms are from benzimidazole rings (the data of hydrogen bonds being given in Table
S4). In the CꢀHꢂꢂꢂπ contacts, the hydrogen atoms are from benzimidazole rings and π
systems are from benzene groups of quinoxalines (the data of CꢀHꢂꢂꢂπ contacts being
given in Table S5). In addition, 2D supramolecular layers are further extended into 3D
19

supramolecular architecture through new CꢀHꢂꢂꢂF hydrogen bonds (Figure S12(b)). In
the new hydrogen bonds, the hydrogen atoms are from quinoxalines.
In the crystal packing of 2b (Figure S13(a)), 2D supramolecular layer is formed
3
through πꢀπ stacking interactions from intermolecular benzimidazole rings.
Interestingly, 2D supramolecular layers are further extended into 3D supramolecular
architecture (Figure S13(b)) through new πꢀπ stacking interactions from
intermolecular benzimidazole rings (the data of πꢀπ stacking interactions being given
in Table S5).
In the crystal packing of 2c (Figure S14(a)), 2D supramolecular layer is formed
through πꢀπ stacking interactions from intermolecular benzimidazole rings (Table S5).
In the crystal packing of 2d (Figure S15(a)), 2D supramolecular layer is formed
by πꢀπ stacking interactions from intermolecular pyridine rings and CꢀHꢂꢂꢂπ contacts.
In this CꢀHꢂꢂꢂπ contacts, the hydrogen atoms are from benzimidazole rings and π
systems are from the benzene rings of quinoxalines. Additionally, the anionic unit
2
ꢀ
[
NiCl ] are packed between successive 2D supramolecular layers and hold layers
4
4
together via CꢀHꢂꢂꢂCl hydrogen bonds to form 3D supramolecular architecture
2 2
(Figure S15(b)). In the hydrogen bonds, the hydrogen atoms are from CH of PyCH
2
ꢀ
4
and chlorine atoms are from [NiCl ] .
References
1
2
3
4
Wei, W.; Wu, M. Y.; Huang, Y. G.; Gao, Q.; Jiang, F. L.; Hong, M. C. Z. Anorg.
Allg. Chem. 2008, 634, 2623.
Bettens, R. P. A.; Dakternieks, D.; Duthie, A.; Kuan, F. S.; Tiekink, E. R. T.
CrystEngComm 2009, 11, 1362.
Chong, Y. S.; Carroll, W. R.; Burns, W. G.; Smith, M. D.; Shimizu, K. D. Chem. Eur.
J. 2009, 15, 9117.
Cole, M. L.; Junk, P. C. CrystEngComm 2004, 6, 173.
20

Table S4. HꢀBonding geometry (Å, ˚) for complexes 2a and 2d
Complexes
DꢀHꢂꢂꢂA
DꢀH
HꢂꢂꢂA
DꢂꢂꢂA
DꢀHꢂꢂꢂA
i
C(6)ꢀH(6)ꢂꢂꢂF(11)
0.929(5)
0.929(5)
0.930(4)
0.988(1)
2.423(2)
2.444(2)
2.437(2)
2.690(2)
3.269(5) 151.2(3)
3.254(6) 145.5(3)
3.202(5) 139.4(2)
3.656(1) 165.6(6)
ii
2
2
a
C(16)ꢀH(16)ꢂꢂꢂF(8)
ii
C(9)ꢀH(9)ꢂꢂꢂF(12)
ii
d
C(6)ꢀH(6A)ꢂꢂꢂCl(2)
Symmetry code: i: 1 + x, 0.5 + y, 1.5 ꢀ z; ii: 1.5 ꢀ x, ꢀ y, ꢀ0.5 + z for 2a. ii: 0.5 + x, 0.5
+
y, ꢀ1 + z for 2d.
Table S5. Distances (Å) of πꢀπ interactions, and distances (Å) and angles (°) of
CꢀHꢂꢂꢂπ contacts for 2a-2d
πꢀπ
CꢀHꢂꢂꢂπ
Complex
Faceꢀtoꢀface
Centerꢀtoꢀcenter
Hꢂꢂꢂπ
CꢀHꢂꢂꢂπ
143.5(2)
_
2a
_
_
2.891(4)
_
2b
3.484(7) (benzimidazole)
3.894(3) (benzimidazole)
3.601(4) (benzimidazole)
3.616(4) (benzimidazole)
3.787(1) (pyridine)
3
.441(8) (benzimidazole)
2
2
c
3.463(9) (benzimidazole)
3.579(1) (pyridine)
_
_
d
3.174(1)
106.4(5)
Figure S12(a). 2D supramolecular layer of 2a via CꢀHꢂꢂꢂF hydrogen bonds and
CꢀHꢂꢂꢂπ constacts. All hydrogen atoms except those participating in the
CꢀHꢂꢂꢂF hydrogen bonds and CꢀHꢂꢂꢂπ constacts were omitted for clarity.
21

Figure S12(b). 3D supramolecular architecture of 2a via CꢀHꢂꢂꢂF hydrogen bonds and
CꢀHꢂꢂꢂπ constacts. All hydrogen atoms except those participating in the
CꢀHꢂꢂꢂF hydrogen bonds and CꢀHꢂꢂꢂπ constacts were omitted for clarity.
Figure S13(a). 2D supramolecular layer of complex 2b via πꢀπ interactions. All
hydrogen atoms were omitted for clarity.
22

Figure S13(b). 3D supramolecular network of complex 2b via πꢀπ interactions. All
hydrogen atoms were omitted for clarity.
Figure S14(a). 2D supramolecular layer of complex 2c via πꢀπ interactions. All
hydrogen atoms were omitted for clarity.
23

Figure S15(a). The 2D supramolecular layer of complex 2d via CꢀHꢂꢂꢂπ constacts and
πꢀπ interactions. All hydrogen atoms except those participating in the CꢀHꢂꢂꢂπ
constacts were omitted for clarity.
Figure S15(b). 3D supramolecular architecture of complex 2d via CꢀHꢂꢂꢂCl
hydrogen bonds, CꢀHꢂꢂꢂπ constacts and πꢀπ interactions. All hydrogen atoms
except those participating in the CꢀHꢂꢂꢂCl hydrogen bonds and CꢀHꢂꢂꢂπ
constacts were omitted for clarity.
24